Startup.cs

using CursoAngularNETCoreHdeleon.Models;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.SpaServices.AngularCli;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace CursoAngularNETCoreHdeleon {

    public class Startup {

        public Startup(IConfiguration configuration) {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services) {
            services.AddControllersWithViews();

            // In production, the Angular files will be served from this directory
            services.AddSpaStaticFiles(configuration => {
                configuration.RootPath = "ClientApp/dist";
            });

            var connection = @"Server=DESKTOP-UCSLS7M; Database=CursoAngularNETCoreHdeleon; Trusted_Connection=True; ConnectRetryCount=0";
            services.AddDbContext<MyDbContext>(option => option.UseSqlServer(connection));
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env) {
            if (env.IsDevelopment()) {
                app.UseDeveloperExceptionPage();

            } else {
                app.UseExceptionHandler("/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();

            if (!env.IsDevelopment()) {
                app.UseSpaStaticFiles();
            }

            app.UseRouting();

            app.UseEndpoints(endpoints => {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller}/{action=Index}/{id?}");
            });

            app.UseSpa(spa => {
                // To learn more about options for serving an Angular SPA from ASP.NET Core,
                // see https://go.microsoft.com/fwlink/?linkid=864501

                spa.Options.SourcePath = "ClientApp";

                if (env.IsDevelopment()) {
                    spa.UseAngularCliServer(npmScript: "start");
                }
            });
        }

    }

}